Alternanthera philoxeroides (Mart.) Griseb.


Alternanthera philoxeroides is an emergent or rooted floating plant that invades aquatic areas and adjoining uplands throughout the southern portions of the United States. Plants have hollow stems and can grow to 3 ft. (1 m) tall.
Opposite, elliptical leaves are thick but non-succulent and are up to 4 in. (10 cm) long.
Flowering occurs during the summer with white, clover-like heads in the axils of the leaves.
Fruits are very small, and single-seeded.
Ecological Threat
Alternanthera philoxeroides roots in wet soils or shallow water and grows out into waterways. Alternanthera philoxeroides can also grow terrestrially, forming smaller, tougher leaves. The thick mats can displace native vegetation and wildlife habitat, clog waterways, restrict oxygen levels of water, increase sedimentation, interfere with irrigation and prevent drainage. It is native to South America and was first introduced into the United States around 1900 in ballast water.


Selected Images


EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit

State Regulated List
   No Data for this state
   Troublesome or Common weed in one or more crops

Most Troublesome / Most Common Agricultural Weed List
This map identifies those states that consider this species either most troublesome or most common in at least one commodity. For more information, visit the MTMC project page.

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Caryophyllidae
Order: Caryophyllales
Family: Amaranthaceae
Genus: Alternanthera
Subject: Alternanthera philoxeroides (Mart.) Griseb.

Synonyms and Other Names

Other Common Names:
alligator weed, pig weed

Related Scientific Names:
Achyranthes philoxeroides (Mart.) Griseb. (Synonym)


Plants - Aquatic Plants